1. Field of the Invention
The present invention relates to a constant-speed cruising system for a vehicle, adapted to automatically control a vehicle speed governing mechanism of an engine so as to reach a target vehicle speed set by the driver.
2. Description of Related Art
For the engine of an Otto type, for example, it is common that a constant-speed cruising system for the vehicle is designed to subject a vehicle speed governing mechanism such as a throttle valve and so on to feedback control on the basis of output from a vehicle speed detecting means for detecting an actual vehicle speed.
Japanese Utility Model Examined Publication (Kokoku) No. 10,361/1984 discloses a constant-speed cruising system in which a microcomputer is used as a control unit for constant-speed cruising control. This constant-speed cruising system has a set switch and a cancel switch as instruction signal outputting means to be outputted to the control unit. The set switch has the function to set an actual vehicle speed to a target vehicle speed for constant-speed cruising control at the time when the driver has turned the set switch on. When the set switch has been turned on, the control unit is designed so as to adjust the actual vehicle speed to reach a target vehicle speed by accumulating a necessary amount of data on vehicle speeds from the vehicle speed sensor and setting a mean value of the vehicle speeds to the target vehicle speed.
The constant-speed cruising system is provided with a main switch for supplying electricity to the control unit. When the main switch is turned on, it is common that the self-diagnosis of the microcomputer disposed therefor is executed or various data stored is initialized.